Walker is among a dozen instructors investigated in the sex scandal at Lackland, one of the nation’s busiest military training centers. Walker faces the most serious charges; among the 28 counts against him are charges of rape, aggravated sexual contact and multiple counts of aggravated sexual assault.

The alleged incidents occurred between October 2010 and June 2011 according to an Air Force statement released Monday. If convicted, Walker faces a potential dishonorable discharge and life in prison.

A military spokeswoman said no testimony was expected at Monday’s hearing and that it would primarily deal with procedural matters.

But the 10 female recruits Walker is accused of either sexually assaulting or engaging in inappropriate sexual conduct with are expected to testify. A seven-member jury made up of military personnel will decide the case.

According to Walker’s Air Force charge sheet cited by The Associated Press, he allegedly had sex with four female recruits, but also groped others, made sexually suggestive comments to them and sent them inappropriate text messages.

Walker is accused of telling one recruit to “get naked” and that she “turned him on,” forcing five recruits to engage in sexual acts by threatening their military careers, and intimidating two of the women into lying about his alleged misconduct, according to the charge sheet.

At least 31 female trainees have been identified as victims in the overall scandal.

Maj. Gen. Margaret H. Woodward has also launched an independent investigation into alleged abuses at the base, which were first reported last year but date back to 2009.

The first court-martial in the case resulted in a plea agreement in June. Staff Sgt. Peter Vega-Maldonado first admitted to having sex with a female trainee and was sentenced to three months’ confinement, then he later acknowledged that he had been involved with 10 trainees.